“You can’t beat the view,” astronaut George Clooney says to NASA scientist Sandra Bullock as they gaze from their space station at the Earth, 372 miles below. Gravity enjoyed a similarly lofty view this weekend, earning $55.6 million at North American theaters, according to preliminary studio estimates.

If that number holds, Alfonso Cuarón’s space epic will set the opening-weekend record for what Box Office Mojo designates as a “fall release” (Sep.–Oct.), ahead of the $52.6 for Paranormal Activity 3 in 2011, the $50.4 million for Jackass 3D in 2010 and the $49.5 million for Taken 2 last year. And unlike those disposable sequels, the utterly original Gravity may be ready to rocket through the autumn and into the awards season.

[UPDATE: According to final weekend figures, issued Monday, Gravity earned $55.8 million, even better than the number announced on Sunday. Cloudy With a Chance of Meatballs 2 took in $20.95 million, down $550,000 from its early estimate. All other movies in the top 10 finished within 2% of their predictions.]

Particularly heartening for Hollywood was that 80% of the first three days’ haul came from theaters showing the movie in 3-D. That topped the percentage for two earlier digital mind-blowers, Avatar (72%) and Life of Pi (68%). People had to see Gravity, and most of them had to see it in 3-D; so after years when the stereoptic novelty seemed to be fading, they paid the $3-4 surcharge for the funny glasses. Overseas, 70% of the $27.4 million that Gravity earned came from 3-D.

IMAX theaters contributed $11.2 million, or about 20% of the take, from just 323 theaters. Audiences were lured by the memory of old IMAX docs, plus movie stars. “A lot of people who grew up going to see IMAX space documentaries like Space Station and Hubble 3D,” Greg Foster, chairman and president of IMAX Entertainment told Variety, “made the connection to see this film also in IMAX.”

Gravity also proved the power of movie stars if they’re in the right vehicle — for example, a space station. The picture marked career-high first weekends for both lead players. Clooney’s previous best was the otherwise forgettable Batman and Robin, which opened to $42.9 million in 1997 (though that figure in today’s dollars would be about $76 million). Bullock topped the $39.1 million for this summer’s The Heat, but she’s been on a roll for the past four years: The Proposal, The Blind Side and The Heat have grossed $580 million at North American theaters, making the 49-year-old perhaps the most reliable marquee draw of her gender.

Budgeted at $100 million, the picture had a hard time finding a home studio, until David Heyman, who had hired Cuarón to direct the third Harry Potter film, came on board as producer and Gravity landed at Warner Bros. From the moment of its Aug. 28 world premiere at the Venice Film Festival, the movie broke through the stratosphere of critical acclaim. It has garnered a 98% “fresh” score from Rotten Tomatoes, which divides reviews by a simple Yes or No system. On Metacritic, which calibrates each review’s level of enthusiasm, Gravity gets a 96 — the all-time high for a film in wide release.

For once, critics and audiences agree: Gravity earned a lofty A-minus grade in the CinemaScore survey of early attendees. The first-weekend crowd skewed male (54%) and mature (59% age 35 and above), indicating long legs for the movie as word-of-mouth spreads. In fact, the good word began over the weekend, with Fri.’s $16.1-million take ballooning to Sat.’s $23 million; and it could keep growing until Oscar night. A guess at the current over-under for the movie’s Academy Award wins would be about six, mostly technical citations. Can Cuarón, Bullock and the film itself also win? Can Warner Bros. repeat the Oscar success it reaped with Ben Affleck’s Argo, which opened a year ago next week? We’ll get back to you in five months.

The weekend’s only other wide release finished far out of the money. Runner Runner, starring Justin Timberlake and Affleck, opened to a snake-eyes $7.6 million. Budgeted at $30 million, the gambling-crime thriller pulled a near-failing “C” from the CinemaScore pollees. On the bright side, the movie has already earned $23.5 million abroad — or, as they say in the online gambling community, offshore.

In a medium-size release, at 387 theaters, the Latino-angled comedy Pulling Strings managed a decent $2.5 million. All in all, though, the weekend was down 20% from the same time last year, when Taken 2 led a strong pack. Only Cuarón’s movie and Cloudy With a Chance of Meatballs 2, in its second weekend, earned as much as $8 million. As moviegoers followed Bullock and Clooney to the stars, and Cloudy into the cartoon sky, the other contenders plummeted. That’s another law of box-office gravity.

Here are the Sunday estimates of this weekend’s top-grossing pictures in North American theaters, as reported by Box Office Mojo: